1. Technical Field
This invention relates to an apparatus for continuous high temperature gas treatment of particulate matter, in which a fluidized bed and a moving bed are continuously formed during the operation of the apparatus; and a method for treating particulate matter with the use of the treatment apparatus.
2. Description of the Related Art
High temperature gas treatment, such as drying, firing, calcination, or high temperature gas reaction, of organic or inorganic particulate matter is performed usually by bringing starting particulate matter into contact with an atmosphere gas, such as air, nitrogen, steam, a combustion gas, or a reactant gas, for a certain period of time at a high temperature of 100 to 3000° C. The mode of contact between the particulate matter and the treating gas is, for example, a fixed bed mode as in a tunnel furnace, a moving bed mode as in a rotary kiln, or a fluidized bed mode such as a stirred bed and an air bubble fluidized bed. In the case of the fixed-bed or moving-bed contact mode, a temperature distribution is apt to occur within each bed, thus rendering uniform contact between the particulate matter and the gas difficult. In the case of the fluidized-bed contact mode, on the other hand, there is an improvement in the temperature distribution or the gas contact, but a completely mixed state is achieved within the bed. During continuous operation, therefore, a treating time distribution occurs and tends to bring a nonuniform product (see “Kagaku Kogaku Binran, Kaitei 6-pan” (A Guide to Chemical Engineering, Revised 6th Ed.), page 458, edited by the Society of Chemical Engineers, Japan, published by Maruzen Co., Ltd.). Thus, a batch operation is usually performed frequently.
If the batch operation is performed using the fluidized bed, uniform treatment becomes possible. However, the operation performed is such that after the starting material is charged into the furnace, the furnace is heated to initiate the reaction and, after completion of the reaction, the furnace is cooled, followed by discharging the treated material. This requires that the temperature of the apparatus be raised or lowered for each batch, entailing great losses not only in time, but in energy. Moreover, thermal stress and strain due to such temperature changes occur repeatedly, tending to pose a problem such as deterioration of the structural material of the furnace.
A known effective way of obtaining a uniform product with the use of the continuous fluidized bed is to provide the apparatuses at multiple stages in series in the direction of a treatment flow so that mixing in the direction of the treatment flow will be decreased to narrow the residence time distribution within the apparatus (see Terukatsu Miyauchi, “Shin-Kagaku Kogaku Koza 14 “Ryukei Sosa to Kongou Tokusei” (A New Course in Chemical Engineering, 14, “Operation of Flow System and Mixing Properties”), pages 10-12, page 24, Nikkan Kogyo Shimbunsha Ltd. (Business & Technology Daily News) (1960)). In order to obtain uniform treatment as obtained with batch operation, however, the provision of the apparatuses in multiple stages as many as several tens of stages or more is needed, and this is impractical.
As described above, uniform high temperature gas treatment has hitherto required either the batch operation, or the provision of the apparatuses in multiple stages in a continuous system. This has presented difficulty in performing an operation for bringing the particulate matter and the treating gas into uniform contact for a certain period of time at a certain temperature.    Non-patent document 1: “Kagaku Kogaku Binran, Kaitei 6-pan” (A Guide to Chemical Engineering, Revised 6th Ed.), page 458, edited by the Society of Chemical Engineers, Japan, published by Maruzen Co., Ltd.    Non-patent document 2: Terukatsu Miyauchi, “Shin-Kagaku Kogaku Koza 14 “Ryukei Sosa to Kongou Tokusei” (A New Course in Chemical Engineering, 14, “Operation of Flow System and Mixing Properties”), pages 10-12, page 24, Nikkan Kogyo Shimbunsha Ltd. (Business & Technology Daily News) (1960)